Process and arrangement for proportioning viscous material

ABSTRACT

In order to obtain an optimal application of viscous material, such as an adhesive or a sealing agent. The process and apparatus combines the proportional metering device and the outlet valve to form a constructional unit. A static mixing tube is integrated into the filling opening. The feed pipe is partially tempered and therefore maintains the viscous material situated in the feed pipe at a constant temperature.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a process for proportioning thick matter suchas a viscous material which is delivered under pressure from a supply,is then proportioned and is applied by way of a controlled outlet valveto an application point and to an arrangement for proportioning viscousmaterial, consisting of at least one storage container and a feed pumpwhich is connected with a proportional metering device by way of a feedpipe as well as of a controlled outlet valve.

In many fields of technology, particularly in the automatedmanufacturing of motor vehicle bodies, it is required to apply viscousmaterial, particularly sealing agents and adhesives, to certainsurfaces. For example, in the case of motor vehicles, threads or thinstrips of sealing agents or adhesives are applied along edges, lockseams or seams of motor vehicle body parts.

This application can take place manually as well as by programmedautomatic manipulating machines, as described, for example, in GermanPatent document DE-C 32 36 647.

In practice, considerable difficulties with such application operationsare encountered because, on the one hand, a fast manufacturing isdesired and, on the other hand, a sufficient application, which is asuniform as possible, of the viscous material is required. In this case,it should be taken into account that the same types of viscous materialwill often have different flow properties because of a differentviscosity, specifically also when this is viscous material from the samemanufacturing batch which is processed within a very short time. Thisconsiderably impairs the uniform delivery of the viscous material or adelivery which can be changed in a proportioned manner.

Despite large expenditures, the known arrangements which have verysensitive control circuits do not constantly achieve the desired resultbecause of their high susceptibility.

There is therefore needed a process and an arrangement by which the flowproperties of viscous material are influenced in a simple manner suchthat, when the nozzle openings have the same sizes, the same quantitiescan always be delivered per unit of time.

According to the invention, these needs are met by a process andapparatus for proportioning viscous material which is delivered underpressure from a supply, is then proportioned and is applied by way of acontrolled outlet valve to an application point. The proportioning takesplace directly in front of the outlet valve separately for each quantityto be applied. Because of the fact that the outlet valve and theproportioning are directly connected with one another, it is possible toproportion immediately before the application and to then dischargedirectly. This will eliminate the previous long flow paths between theproportioning and the outlet valve which have led to inaccuracies of theoutflow rate per unit of time. This also eliminates the additional feedpipes. Another advantage is the fact that the viscous material to bedischarged can be sufficiently mixed or sheared immediately during thefilling of the proportioning device.

A reinforcement of the mixing device or the shearing of the viscousmaterial is achieved by providing a mixing section, for example, astatic mixer tube can be installed in the inlet of the proportioningdevice.

In a further particularly advantageous embodiment of the process theproportioning takes place by means of a purely volumetric control inthat, in the case of deviations in the application quantity during onedischarge operation, the subsequent discharge operation is controlled toa desired value. This embodiment minimizes the control expenditures andnevertheless achieves excellent results.

By means of the further development, viscosity differences caused bytemperature changes are avoided.

A still further development has the advantage that the previously knownswitching valve at the outlet of the proportional metering device can beeliminated and the outlet valve can be connected directly to thedelivery chamber of the proportional metering device. This furtherminimizes the control expenditures.

Another development according to the invention achieves the advantagethat the viscous material is continuously delivered into theproportional metering device so that viscous material does not have tobe stored there for extensive waiting periods which, in turn, wouldresult in differences in viscosity. This ensures that there issufficient mixing and shearing immediately before the application of theviscous material.

In a further development according to the invention, the differences inviscosity resulting from variations in temperature are avoided. In thiscase, it is not required to temper the whole feed pipe between thestorage container and the proportional metering device. It is sufficientto temper thirty (30) times the application volume. "Tempering" in thiscase is the achieving of a constant temperature; that is, a heating orcooling depending on the environmental influences.

The further development according to the invention describes a preferreddevelopment for the tempering. In this case, it was also found to beeffective to include the proportional metering device and the outletvalve.

The present invention describes a simple possibility of providing avolumetric control.

By means of the pressure relief of the flow rates during productionstoppages, the thixotropy can be kept constant.

By further developing the invention, the mixing and flexing of theviscous material to be proportioned will be promoted further.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an arrangement of a system forproportioning viscous material according to the present invention; and

FIG. 2 is a schematic cross-sectional view of the proportional meteringdevice with a flanged-on outlet valve according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The invention will be explained by way of the application of an adhesiveto a component 1 which may, for example, be part of a motor vehicle. Ofcourse, the invention is applicable to other components as well.

The adhesive is provided in two barrels 2 and 3. Each barrel is providedwith a feed pump 4, 5. Their two delivery pipes meet in junction 6 fromwhich a return pipe 7, 8 also branches off which leads to each barrel 2,3. A pressure relief valve 9, 10 is also installed in each return flowpipe. Both feed pumps 4, 5 are operated successively such that deliveryonly takes place to one barrel at a time.

A feed pipe 11 extends from the junction 6 to a proportional meteringdevice 12.

During the stoppage/readiness time of the system, the feed pipe 11 canhave its feed pressure relieved by the pressure relief valves 9, 10 sothat a constant thixotropy is achieved.

The proportional metering device 12 is directly connected with an outletvalve 13. Both the proportional metering device 12 and the outlet valve13 are carried by an automatic manipulator 14 and are guided inaccordance with a preprogrammed path along the application surfaces ofthe workpiece 1. The control of the proportional metering device 12 andthe outlet valve 13 takes place by way of the controlling of theautomatic manipulator 14 so that no separate control is required.

A portion of the length of the feed pipe 11 as well as the proportionalmetering device 12 and the outlet valve 13 are a component of a heattransfer circulation system 15. This heat transfer circulation system 15contains a heating device 16 as well as a recooling device 17 and a feedpump (which is not shown in detail). As a result, it is possible toalways keep the adhesive at a constant temperature.

As clearly illustrated in FIG. 1, the whole feed pipe 11 is nottempered, but rather only a portion thereof. It was found to besufficient to temper approximately thirty (30) times the applicationvolume which, in practice, corresponds to approximately 6 mm of feedpipe.

In FIG. 2, the proportional metering device 12 with the flanged-inoutlet valve is illustrated in detail.

The proportional metering device 12 is driven pneumatically. For thispurpose, it has a piston 18 which is movably arranged in a deliveryspace 19 and is supplied with pressurized air by way of a proportionalvalve 36 in a controlled manner.

The piston is connected with a piston rod 20 and is extended beyond thedelivery space 19 into a metering chamber 22.

The feed pipe 11 is connected to the metering chamber 22 by way of ashut-off valve 23 and a static mixing pipe 35.

An outlet 24 from the metering chamber 22 leads directly into the outletvalve 13 above a valve needle 25. When the outlet valve 13 is open, theadhesive is discharged by way of a nozzle 26.

The outlet valve 13 is also controlled pneumatically. For this purpose,the nozzle needle 25 is connected with a control piston 27 which opensagainst the force of a spring 28. The outlet valve 13 is controlled byway of a 2/2-way valve 29.

For the volume control, the proportional metering device 12 has threeproximity switches 30, 31 and 32 which detect the piston path. In thiscase, the proximity switch 30 detects the inoperative position of thepiston 18. In this position, the shut-off valve 23 can be opened and themetering chamber 22 can be filled.

The proximity switch 31 detects the minimal application amount; that is,when the piston 18 reaches this position, the piston rod 20 has mixedthe adhesive charged in the metering chamber 22 but has pushed out onlya small amount of adhesive by way of the opened outlet valve 13.

The proximity switch 32 characterizes the maximal application amount;that is, when the piston 18 reaches this proximity switch, the pistonrod 20 is situated close to the lower end of the metering chamber 22.Thus, the largest-possible amount of adhesives has been pushed outthrough the opened outlet valve 13.

Correspondingly, the amount of adhesive to be applied can also bemonitored and controlled by way of these three proximity switches. Forthis purpose, the proximity switches 30 to 32 are arranged with respectto one another corresponding to the desired quantity to be applied.When, during an application, the piston reaches a position betweenproximity switch 31 and 32, that is, it overruns the proximity switch31, but does not reach the proximity switch 32, the application quantityis correct.

If the piston 18 reaches only the proximity switch 31, only the minimalquantity has been discharged and the proportioning pressure can beincreased for the subsequent application by way of the proportioningvalve 36.

When, after the application of the adhesive, the piston reaches themaximum switch 32, slightly more than the required amount has beenpushed out. For the next application operation, the proportioningpressure in the delivery space 19 will then be lowered. If, during anapplication operation, the proximity switch 31 is not reached, or thepiston moves farther downward beyond the proximity switch 32, theapplication quantity is incorrect in both cases and the system willreport a disturbance.

FIG. 2 also illustrates a possibility of a tempering also in the case ofthe feed line 11 in that the feed line has a double-walled construction.In this case, a heat transfer medium can then circulate between itsinterior wall 33 and its exterior wall 34 and thus hold this feed linesection at a constant temperature. Naturally, the switching valve 23 canalso be integrated in the heat transfer medium circulation system, aswell as the metering chamber 22 of the proportional metering device andthe area around the nozzle needle 25 of the outlet valve 13.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

What is claimed is:
 1. A process for dispensing viscous material, theprocess comprising the steps of:delivering the viscous material underpressure from a supply; proportioning said viscous material via aproportional metering device immediately upstream of a controlled outletvalve separately for each quantity to be applied; tempering both theproportional metering device and the controlled outlet valve; andsubsequently applying said proportioned and tempered viscous materialfrom said controlled outlet valve to an application point.
 2. Theprocess according to claim 1, wherein prior to said proportioning step,the process includes the step of mixing the viscous material.
 3. Theprocess according to claim 2, wherein said proportioning step furtherincludes the steps of:performing a purely volumetric control such that,in case of deviations in an application quantity during one dischargeoperation, a subsequent discharge operation is controlled to a desiredvalue.
 4. The process according to claim 1, wherein said proportioningstep further includes the steps of:performing a purely volumetriccontrol such that, in case of deviations in an application quantityduring one discharge operation, a subsequent discharge operation iscontrolled to a desired value.
 5. The process according to claim 1,further comprising the step of tempering a feed line along a lengthcorresponding to approximately 30 times an application volume of theproportional metering device between the supply and the proportionalmetering device.
 6. The process according to claim 1, further comprisingthe step of reducing a delivery pressure during a readiness state of thedevice.
 7. An arrangement for dispensing viscous material, comprising:atleast one storage container; a feed pump coupled to said at least onestorage container; a proportional metering device connected to said feedpump via a feed pipe; a controlled outlet valve mounted directly on saidproportional metering device; a tempering unit coupled to temper boththe proportional metering device and the controlled outlet valve;whereby said proportional metering device separately proportions theviscous material immediately upstream of the controlled outlet valve foreach quantity to be applied.
 8. An arrangement according to claim 7,wherein said controlled outlet valve is controlled separately via aswitching valve.
 9. An arrangement according to claim 8, furthercomprising a shut-off valve arranged in said feed pipe upstream of saidproportional metering device.
 10. The arrangement according to claim 8,wherein said feed pipe is tempered approximately 30 times an applicationvolume of the proportional metering device beginning at saidproportional metering device and extending upstream.
 11. An arrangementaccording to claim 7, further comprising a shut-off valve arranged insaid feed pipe upstream of said proportional metering device.
 12. Thearrangement according to claim 11, wherein said feed pipe is temperedapproximately 30 times an application volume of the proportionalmetering device beginning at said proportional metering device andextending upstream.
 13. The arrangement according to claim 7, whereinsaid feed pipe, is tempered approximately 30 times an application volumeof the proportional metering device beginning at said proportionalmetering device and extending upstream.
 14. The arrangement according toclaim 13, wherein said tempering comprises a heat transfer mediumcirculation system in which heating and cooling devices for a heattransfer medium are installed.
 15. The arrangement according to claim 7,wherein said proportional metering device with said controlled outletvalve is integrated in the tempering device comprised of a heat transfermedium circulation system.
 16. The arrangement according to claim 7,wherein said proportional metering device is equipped with a strokecontrol.
 17. The arrangement according to claim 7, wherein a pressurerelief valve is installed in said feed pipe.
 18. The arrangementaccording to claim 7, wherein a static mixing tube is provided between ashut-off valve and a metering chamber.